Recently, I had the opportunity to observe additional bird species collecting nectar from the African Tuliptree (Spathodea campanulata), a common ornamental species in the region. The bird species collecting nectar from this tree included Orchard Orioles (Icterus spurius),

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…Hooded Orioles (Icterus cucullatus),

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…and Yellow-winged Caciques (Cassiculus melanicterus).

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All of the above species are well-documented nectar collectors.1

The final bird I saw collecting nectar — the Rufous-backed Robin or Thrush (Turdus rufopalliatus) — was a considerably bigger surprise.

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While many of the True Thrushes, including Rufous-backed Robins, consume significant amounts of fruit, I could only find one record of them consuming nectar. An unpublished source indicates that Asian species, the Grey-sided Thrush (Turdus feae), collects nectar from the flowers of the legume Acrocarpus fraxinifolius.2

So why would birds that eat sugar-rich fruit rarely if ever take the opportunity to collect similarly sugar-rich nectars? Apparently, the answer to this question lies in the kinds of sugars found in fruit and nectar.3

The sugars in fruit are almost always glucose and fructose. These sugars are simple and directly absorbed in the intestines of frugivores without need of further processing. Conversely, most floral nectars have sucrose as their predominant sugar. Sucrose is a disaccharide formed from glucose and fructose and cannot be absorbed by the intestines until it is broken down into glucose and fructose by the enzyme sucrase.

There are, however, some plants that produce floral nectars where glucose and fructose are the predominant sugars.3 Such plants are more common in the Old World than in the New. This may be the result of a more equitable sharing of the avian nectar-feeding niche in the Old World between passerine species that can and can’t digest sucrose. In the New World, sucrose-digesting hummingbirds dominate this niche possibly reducing the selection for plants that produce floral nectars rich in glucose and fructose rather than sucrose.

This then may explain why I was able to observe Rufous-backed Robins feeding on nectar. The tree they were collecting nectar from, the African Tuliptree, is one of those Old World species whose nectar contains glucose and fructose instead of sucrose.4

As always, one question answered leads to others. Is this a relatively new behavior for Rufous-backed Robins or have we managed not to see them collecting nectar from other native plant species whose nectars contain glucose and fructose instead of sucrose? Also, the calyces of the African Tuliptree produce large quantities of water which are necessary for floral development and which then spills over into the opening flowers. In the relatively xeric environment along this part of the west coast of Mexico, has this unusual feature played any role in the origin and maintenance of nectar feeding in this thrush?

One of the more lovelier birds in west Mexico is the west Mexican endemic, the Russet-crowned Motmot (Momotus mexicanus), shown below with a cockroach.

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It was my good fortune to watch a breeding pair provisioning their offspring from around the middle of June to the beginning of July. I took pictures and made videos. While doing this, I was reminded of something I read in John Terborgh’s book Diversity and the Tropical Rainforest.1 In his book Terborgh argues that one component of increased biological diversity in tropical rainforests as compared to elsewhere is a greater number of niches. One such niche created by the presence of large tropical rainforest insects is the large tropical rainforest insect eating guild of birds, exemplified by the motmots.

While this wasn’t the rainforest and the insects and other things brought back to the nest weren’t all big, it was nevertheless an interesting assortment of food items. Because motmots nest in burrows and the chicks are hidden away, I couldn’t see them receiving their meals. Suffice it to say, though, for a motmot chick a meal can be a real surprise!

Caterpillars are an important nestling food source for neotropical migrants. For the photographed pair of Russet-crowned Motmots, they were important too. At times it appeared that the pair identified a particular caterpillar host plant and returned to that plant repeatedly for the same species of caterpillar. The first of three caterpillar photographs is also further evidence that the eversible osmeterium (the yellow “horn-like” projection arising from just behind the head) of swallowtail butterfly larvae, while secreting substances that deter ant and other invertebrate predators, is relatively ineffective against vertebrate predators.2

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The motmot pair also commonly fed their offspring adult cicadas and less commonly juvenile forms (the first photo).

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Beetles too were important components of the nestling’s diet. In the early part of my observations, elongate beetle larvae like the one shown in the last picture were frequently brought back to the nest.

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The adult pair also fed their nestlings an assortment of other animal foods including, among other things, ant alates, millipedes, crabs, snakes, frogs, and terrestrial slugs. The last photograph shows a bird with a vertebrate whose tail is missing although I can’t tell if it’s a lizard or young mammal.

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Finally, fruit – particularly guamuchiles (Pithecellobium dulce) shown in the first photograph – was also an important component of offspring diet.

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These photographs show that Russet-crowned Motmots feed their nestlings a variety of foods from locations as diverse as the crowns of trees to leaf litter on the ground. They also provide additional evidence that the assumed chemical defenses of things like papilionid larvae2 and millipedes3 often do not deter bird predation.

In August of 2017 I began to photograph and identify flowering plants at Cuixmala and the Fundación Ecológica de Cuixmala. To help with identification, I relied heavily on two area plant lists to narrow down the possibilities. Both of these were produced by the preeminent plant taxonomist for the Chamela-Cuixmala area, Dr. Emily J. Lott.

Initially I used her list found at the Estacion Chamela website (http://www.ibiologia.unam.mx/ebchamela/www/flora.html) but later used the more recent and extensive one she published in 2002 in the book Historia Natural de Chamela (HNC). Nevertheless, in the course of identifying what the HNC list suggested would be about 10% of the species present in the area, I had already found 4 species “new” to the area (Funastrum bilobum, Hibiscus colimensis, Nama jamaicensis, and Solanum angustifolium).

Also, while doing the identifications, it was apparent that there had been numerous taxonomic changes. Many of these were the result of revolutionizing molecular phylogenies published since 2002.

Consequently, I decided to update Lott’s HNC list, at least for the “traditional dichots”.

In June of 2015, below the ostentatious facade of Casa Cuixmala and amidst the property’s exotic cast of zebras and impalas, my daughter and I were privileged to witness something truly elegant and special on an otherwise obscure liana (Paullinia fuscescens) growing along one of the trails:

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Neoponera ants and the vast majority of paper wasp species are powerful insect predators.[1],[2] Such seemingly placid interactions between them and their potential prey might initially bring to mind the idyllic scene foretold by the Old Testament prophet Isiah :

The wolf and the lamb shall graze together; the lion shall eat straw like the ox…

Doing a morning walk in Cuixmala on the trail along the Pistia-filled lake near Carretera 200 (across from the fundación), I came across something “floating” in the air in front of me. Usually this is a caterpillar hanging by one of its silken threads. As can be seen in these photos, that wasn’t the case here:

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Crab spiders (Family Thomisidae) are incredible in taking on larger and seemingly dangerous prey like this paper wasp (Polistes dorsalis) without the assistance of a web. Instead, they hang out motionlessly and frequently camouflaged at flowers or on leaves with fallen flowers. Here, they pounce on their prey and hold them with their first two pairs of legs while biting and injecting venom. Crab spiders are not dangerous to humans but you have to think that their venom is pretty powerful.

What happened here? While paper wasps don’t collect pollen to feed their offspring, they do occasionally visit flowers to feed on their nectar. They also search plants for caterpillars and other insects that they feed their offspring. For whatever reason, this one got too close to a crab spider.

While crab spiders don’t build webs, they still make and use silk. Normally eating their prey where they catch them, this one shot a line of silk out and left its perch with the wasp in its chelicerae (jaws). We can’t know exactly why it did this but perhaps a large ant or some other dangerous animal or potential predator got too close.

While the crab spider in the photos is holding the paper wasp by the base of its head, this doesn’t mean that’s where it delivered its deadly bite. Crab spiders prefer to feed from the head where they inject digestive enzymes and then suck up the slurry. What they suck up from the head must be very good. One study of crab spiders feeding on fruit flies showed that they always started at the head and then switched to the abdomen to complete their meal. If, however, a new fly appeared while a crab spider was feeding from the head of a captured fly, the spider would prefer trying to catch another fly rather than finish its meal at the other end of the captured one.

Anyway, shortly after the last picture the crab spider fell to the ground with its paper wasp where I presume it finished its meal.